Ameren Missouri Files for 10.6 GW of New Gas, Inverting Last Year’s 60 Percent Clean Target for 2045
- Policy & Markets Regulatory State & Local Regulation
Marin Holt
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- 9 minutes read
- New gas capacity: 10.6 GW
- Battery storage by 2030: 2,400 MW
- Gas share of mix by 2045: 60 percent
- Large-load agreements signed: 2.8 GW
- Labadie coal units retire: 2042
Ameren Missouri filed a 20-year integrated resource plan with the Missouri Public Service Commission on Monday, September 28, 2026. The utility serves about 1.3 million customers across central and eastern Missouri. Its preferred plan adds 10.6 GW of new natural gas capacity, 3.6 GW of solar, 2.4 GW of battery storage, 1.5 GW of wind and 1.2 GW of nuclear. Gas supplies about 5 percent of the company’s generation mix today. Under this plan gas reaches 60 percent by 2045, and coal falls to zero.
Last year’s plan pointed the other way. It had renewables and nuclear supplying 60 percent of generation by 2045. The 2026 filing moves that 60 percent share to gas instead. Ameren told regulators it picked this plan from more than 20 candidates.
Why It Matters
Large loads drive the reversal. Ameren has signed electric service agreements totaling 2.8 GW of expected demand by the end of the decade. That is almost double the 1.5 GW its 2025 expectations carried. The utility told regulators that large loads will grow base customer deliveries by 60 percent between 2027 and 2030, and it forecasts annual sales growth of 5 to 6 percent across the plan. Large-load deliveries run about 1,400 GWh in 2027 and reach 44,676 GWh by 2046 in the base case, a compound annual growth rate of 20 percent.
Ameren writes that Missouri law and its own practices make large loads cover the cost of infrastructure built to serve them. Residential customers are already absorbing a separate ask. The company filed for a 343 million dollar rate increase in June, which local reporting put at roughly 10 percent on a typical monthly residential bill.
What Ameren Plans to Build
The gas build arrives in blocks. Ameren plans 2,100 MW of combined-cycle capacity in service by 2031, another 2,800 MW by 2035 and 1,400 MW more by 2042. It adds 1,900 MW of simple-cycle gas by 2029 and a further 2,400 MW after 2040. Solar reaches 1,300 MW by 2030. Battery storage reaches 2,400 MW by 2030, the one category where this plan moves faster than its predecessor. Wind waits until after 2030 for its 1,500 MW.
The nuclear line is the thinnest. Ameren assigns 1,200 MW to new nuclear by 2040 and has chosen neither a site nor a reactor technology. The filing says both large reactor designs and small modular reactors remain under consideration. Ameren also expects to seek an extension to run the Callaway plant past 2044.
The Coal Units Stay Longer
Ameren retires Sioux Energy Center by the end of 2035 and all four units at the Labadie Energy Center by the end of 2042. Labadie rates at nearly 2.4 GW. Previous plans closed two of those units by the end of 2036, so the 2026 filing extends them by six years. The plan also preserves options to run Labadie and Sioux longer still.
Environmental groups objected on that point. “The saying goes to stop digging if you’re in a hole, but Ameren is still digging with its pollution-heavy plan even though it admits extreme weather events are increasing,” said Jenn DeRose, the Sierra Club’s Beyond Coal campaign strategist in Missouri.
Enforcement Reality
The plan commits Ameren to nothing. Missouri’s resource-planning rule lets the Public Service Commission acknowledge a utility’s preferred plan, and the rule defines the limit of that act in plain terms. “Acknowledgment shall not be construed to mean or constitute a finding as to the prudence, pre-approval, or prior commission authorization of any specific project or group of projects,” states 4 CSR 240-22.010. The rule also lets the commission grant acknowledgment in whole, in part, or not at all. Ameren files a triennial compliance plan and revises it between filings. Nothing in this filing obliges the company to build that gas fleet, close Labadie on the stated schedule, or reach its storage target.
The documents that bind sit elsewhere. Ameren has already asked state regulators for permission to build a 2.1 GW plant at West Alton under a mechanism that charges customers while construction proceeds. That request carries a cost obligation this resource plan does not.
Ameren’s own filing concedes the ground is unsettled. “Given the lack of certainty regarding future regulatory programs, Ameren Missouri has necessarily made good faith assumptions based upon available information regarding potential future compliance measures,” the plan says, and adds that those assumptions are subject to revision.
Critical Perspective
Ameren tells regulators it will add 10.6 GW of gas and cut coal to zero by 2045. The plan it filed is the one document in this process that obliges nothing, while the 2.1 GW West Alton request already before the Missouri Public Service Commission carries a cost obligation. North Carolina regulators denied Duke Energy a 255 MW gas turbine in September over data-center load growth the company had not verified, which shows that a planning number and an approved plant are different things. If Missouri acknowledges this plan only in part, which gas units does Ameren build anyway?
Sources
- Utility Dive
- Energy Storage News
- St. Louis Magazine
- Ameren Missouri (company filing page)
- Missouri Code of State Regulations, 4 CSR 240-22 (Electric Utility Resource Planning)
